Effects of carbon dioxide inhalation on hematology, coagulation, and serumclinical chemistry values in rats

Blood samples from adult male and female Charles River Crl:CD(R) (SD) BR ra ts were collected at weekly intervals for 4 wk to evaluate the effects of i nhalation of an anesthetic dose of carbon dioxide (CO2) or of a carbon diox ide-oxygen mixture (CO2/O-2) on hematology, coagulation, and serum biochemi stry values. During the first 3 wk of the study, rats were assigned to 1 of 3 groups and were bled from the orbital sinus once weekly. Prior to the bl ood collection, rats in group 1 were exposed to room air only, rats in grou p 2 received CO2/O-2 (approximately 66%:34% CO2:O-2) by inhalation, and rat s in group 3 received 100% CO2 by inhalation. In the rats exposed to CO2/O- 2 or CO2, leukocyte counts, lymphocyte counts, and glucose values were high er, and aspartate aminotransferase, creatine kinase, and calcium values wer e lower compared with those of rats exposed to room air only. Rats exposed to 100% CO2 had slightly (but statistically significant) lower mean corpusc ular hemoglobin concentration when compared with rats exposed only to room air. During week 4, all rats were reassigned to 1 of 2 groups and were bled terminally via closed cardiac puncture following exposure to either CO2/O- 2 or CO2. Increased lymphocyte counts (males only) and glucose and chloride concentrations were noted for rats exposed to CO2/O-2 compared with those exposed to CO2. These alterations reiterate the importance of comparing cli nical pathology values to those of concurrent control groups that have expe rienced blood collection under identical conditions in order to avoid poten tial errors in the interpretation of data.